This invention relates to methods for making aryl hydrazines and substituted indoles, which are useful intermediates and end products in pharmaceutical and agricultural applications.
Certain 3,5-disubstituted indole compounds have been found to be selective agonists which act on 5-hydroxytryptamine receptors and to be useful in the treatment of migrane and other medical conditions, see U.S. Pat. No. 5,607,960.
Syntheses of such indole compounds have typically been based on the approach of functionalizing an existing indole nucleus, necessitating a large number of processing steps and reduced theoretical efficiency for the sequence of steps, see for example, U.S. Pat. No. 5,998,438, which discloses synthesis of 5-(1-Aza-1-methylcyclohex-3-en-4-yl)-3-[2-(N,N-dimethylamino)ethyl]-1-H-indole. The route desclosed in the ""438 patent also requires use of a toxic reagent, that is, 4-tributylstannyl-1-aza-1-tertbutoxycarbonylcyclohex-3-ene, and the use of a hazardous reagent, LAH.
There is an interest in development of a simplified synthetic route to such indole compounds.
In a first aspect, the present invention is directed to a method for making an aryl hydrazine, comprising:
(a) reacting a substrate aromatic compound, said substrate aromatic compound bearing an activated carbon atom, and a hydrazone in the presence of a transition metal catalyst under conditions suitable to form an aryl hydrazone having a new carbon-nitrogen bond between the activated carbon of the substrate aromatic compound and a nitrogen atom of the hydrazone, and
(b) hydrolyzing the aryl hydrazone to form the aryl hydrazine.
The method of the present invention for making an aryl hydrazine provides a simple, two step linear synthesis of substituted aryl hydrazine compounds and does not require the use of toxic or hazardous reagents.
In a second aspect, the present invention is directed to a method for making an indole compound, comprising:
(a) reacting a substrate aromatic compound, said substrate aromatic compound bearing an activated carbon atom, and a hydrazone in the presence of a transition metal catalyst under conditions suitable to form an aryl hydrazone having a new carbon-nitrogen bond between the activated carbon of the substrate aromatic compound and a nitrogen atom of the hydrazone,
(b) hydrolyzing the aryl hydrazone to form an aryl hydrazine, and
(c) cyclizing the aryl hydrazine in the presence of an aldehyde or ketone and acid catalyst to form the substituted indole compound.
The method of the present invention for making an indole compound provides a simple, three step linear synthesis of substituted indole compounds and does not require the use of toxic or hazardous reagents.
In a preferred embodiment, a substrate aromatic compound and a hydrazone are coupled to form a hydrazone according to reaction scheme 1: 
wherein:
Ar is aryl and may, optionally, be further substituted beyond X,
X is a leaving group that is capable of being replaced by a nucleophilic nitrogen in a transition metal-catalyzed arylation reaction, and
R1 is H, substituted or nonsubstituted alkyl, substituted or nonsubstituted alkenyl, substituted or nonsubstituted alkynyl, substituted or nonsubstituted aryl or substituted or nonsubstituted heterocyclyl, and
each R2 is independently H, substituted or nonsubstituted alkyl, substituted or nonsubstituted alkenyl, substituted or nonsubstituted alkynyl, substituted or nonsubstituted aryl or substituted or nonsubstituted heterocyclyl, or, alternatively, the R2 groups are fused to form, together within the carbon atom to which they are each attached, a substituted or unsubstituted monocyclic cycloalkyl, cycloalkenyl, aryl or heterocyclyl ring.
As used herein, the term xe2x80x9csubstitutedxe2x80x9d denotes the conceptual replacement of a hydrogen atom of a given organic moiety with a substituent group other than a hydrogen atom and includes all permissible substituent groups, including acyclic hydrocarbon groups, alicyclic hydrocarbon groups, monocyclic aromatic hydrocarbon groups, polycyclic aromatic hydrocarbon groups, heteroacyclic groups, heterocyclic groups, fused ring systems and bridged ring systems, of which the substituents specifically described below are illustrative examples.
As used herein the term xe2x80x9cheteroatomxe2x80x9d means an element other than carbon, such as for example, oxygen, nitrogen and sulfur.
xe2x80x9cAlkylxe2x80x9d refers to a linear, branched or cyclic saturated hydrocarbon group, preferably a (C1-C30) linear, branched or cyclic saturated hydrocarbon group that may, optionally, contain one or more heteroatoms, such as, for example, methyl, ethyl, propyl, n-butyl, isobutyl, t-butyl, neopentyl, cyclopentyl, hexyl, cyclohexyl, decyl, stearyl, eicosyl, methoxy, triacontyl, 2,5,7-trioxanonanyl, 2,5,8-triazadecenyl, and that may, optionally, be substituted at one or more positions with other moieties, such as, for example, alkyl, alkenyl, alkynyl, aryl, heterocyclyl, halo, hydroxy, sulfhydryl, hydroperoxy, carbonyl-containing groups (including, for example, carboxy, ketone, ester and aldehyde groups), alkyloxy, alkyldioxy, amino, amido, imino, hydrazino, nitro, cyanato, thiocyanato, mercapto, thiocarbonyl-containing groups (including, for example, thioketone groups, thioester groups and thioaldehyde groups), sulfonyl-containing groups (including, for example, sulfate, sulfonate and sulfamoyl groups), silyl, siloxy and phosphoruscontaining substituent groups (including, for example, phosphoranyl, phosphinyl, phosphinothioyl, phosphinimyl). Such substituent groups may themselves be further substituted with, for example, any of the groups described above as suitable substituents for alkyl groups, to form compound substituent groups, such as, for example, aralkyl, aminoalkyl, haloalkyl, heterocyclylalkyl.
xe2x80x9cAlkenylxe2x80x9d refers to a linear, branched or cyclic hydrocarbon group, preferably a (C2-C20) linear, branched or cyclic hydrocarbon group, that contains one or more carbon-carbon double bonds per group and that may, optionally, contain one or more heteroatoms, such as, for example, ethenyl, propenyl, allyl, isopropenyl, ethenylidenyl, cyclopentyl, cyclohexadienyl, azanonenyl, and that may, optionally, be substituted at one or more positions with other moieties, such as, for example, any of the possible substituents described above in respect to alkyl groups.
xe2x80x9cAlkynylxe2x80x9d refers to a linear, branched or cyclic unsaturated hydrocarbon group, preferably a (C2-C20) unsaturated hydrocarbon group, that contains one or more carbon-carbon triple bonds per group and that may, optionally, contain one or more heteroatoms, such as, for example, ethynyl, propynyl, thianonynyl, and that may, optionally, be substituted at one or more positions with other moieties, such as, for example, any of the possible substituents described above in respect to alkyl groups.
xe2x80x9cArylxe2x80x9d refers to an unsaturated hydrocarbon group that contains one or more six membered rings in each of which the unsaturation may be represented by three conjugated carbon-carbon double bonds, including monocyclic and polycyclic ring systems, such as, for example, phenyl, naphthyl, anthryl, phenanthryl, indenyl, fluorenyl, which may, optionally, be substituted at one or more positions with other moieties, such as, for example, any of the possible substituents described above in respect to alkyl groups.
xe2x80x9cHeterocyclylxe2x80x9d refers to a saturated or unsaturated organic group that contains one or more rings in which one or more ring members is a heteroatom, preferably a nitrogen, sulfur or oxygen heteroatom, such as, for example, thiacyclopentadienyl, thiaindenyl, thianthrenyl, oxacyclopentadienyl, oxaindenyl, isobenzylfuranyl, pyranyl, azacyclopentadienyl, pyridinyl, pyrazinyl, pyrimidinyl, pyridazinyl, indolinyl, quinolinyl, isoquinolinyl, phthalazinyl, cinnolinyl, azafluorenyl, phenanthrolinyl, phenazinyl, phenothiazinyl, phenarsazinyl, isothiazolyl, isoxazolyl, phenoxazinyl, pyrrolidinyl, pyrimadinyl, imidazolidinyl, piperidinyl, piperizinyl, oxathiaanthracenyl, isoxazolyl, oxaazaanthracenyl, isothiazolyl, morpholinyl, and which may, optionally, be substituted at one or more positions with other moieties, such as, for example, any of the possible substituents described above in respect to alkyl groups.
As used herein, xe2x80x9chaloxe2x80x9d means fluoro, chloro, bromo or iodo, xe2x80x9chydroxyxe2x80x9d means xe2x80x94OH, xe2x80x9csulfhydrylxe2x80x9d means xe2x80x94SH, xe2x80x9chydroperoxyxe2x80x9d means xe2x80x94OOH, xe2x80x9ccarbonylxe2x80x9d means xe2x80x94C(O)xe2x80x94, xe2x80x9ccarboxyxe2x80x9d means xe2x80x94COOH, a ketone group is a group containing a carbonyl moiety that is attached to two carbon atoms, an ester group is a group containing a xe2x80x94C(O)OR moiety, an aldehyde group is a group containing a xe2x80x94CHO moiety, xe2x80x9calkyloxyxe2x80x9d means xe2x80x94ORxe2x80x2, xe2x80x9calkyldioxyxe2x80x9d means xe2x80x94OORxe2x80x2, xe2x80x9caminoxe2x80x9d is conceptually a derivative of NH3 in which one or more hydrogen atoms are replaced by nonacyl organic groups and includes primary, secondary and tertiary amines, xe2x80x9camidoxe2x80x9d includes, for example, xe2x80x94C(O)NRxe2x80x32, xe2x80x9ciminoxe2x80x9d means xe2x95x90NH, xe2x80x9chydrazinoxe2x80x9d includes, for example, xe2x80x94HNNRxe2x80x32, xe2x80x9cnitroxe2x80x9d is xe2x80x94NO2, xe2x80x9ccyanatoxe2x80x9d is xe2x80x94OCN, xe2x80x9cthiocyanatoxe2x80x9d is xe2x80x94SCN, xe2x80x9cmercaptoxe2x80x9d is xe2x80x94SH, xe2x80x9cthiocarbonylxe2x80x9d is xe2x80x94C(S)xe2x80x94, a xe2x80x9cthioketone groupxe2x80x9d is a group containing a thiocarbonyl moiety that is attached to two carbon atoms, a xe2x80x9cthioester groupxe2x80x9d is xe2x80x94C(S)OR, a xe2x80x9cthioaldehydexe2x80x9d group is a group containing a xe2x80x94CHS moiety, xe2x80x9csulfonylxe2x80x9d is xe2x80x94SO2xe2x80x94, xe2x80x9csulfatexe2x80x9d includes, for example, xe2x80x94OSO2ORxe2x80x3, xe2x80x9csulfonatexe2x80x9d includes, for example, xe2x80x94O2SORxe2x80x3, xe2x80x9csulfamoylxe2x80x9d includes, for example, xe2x80x94O2SNRxe2x80x32, xe2x80x9csilylxe2x80x9d is xe2x80x94SiRxe2x80x33, xe2x80x9csiloxyxe2x80x9d is xe2x80x94OSiRxe2x80x33, xe2x80x9cphosphinoxe2x80x9d includes xe2x80x94PRxe2x80x32, xe2x80x9cphosphoranylxe2x80x9d includes, for example, xe2x80x94PRxe2x80x34,xe2x80x9cphosphinylxe2x80x9d includes, for example, xe2x80x94P(O)Rxe2x80x32, xe2x80x9cphosphinothioylxe2x80x9d includes, for example, xe2x80x94P(S)Rxe2x80x32, xe2x80x9cphosphinimylxe2x80x9d includes, for example, xe2x80x94P(NH)Rxe2x80x32, xe2x80x9caralkylxe2x80x9d means an alkyl group substituted with an aryl group, such as, for example, benzyl, xe2x80x9caminoalkylxe2x80x9d means an alkyl group substituted with an amino group, such as, for example, dimethylaminoethyl, xe2x80x9chaloalkylxe2x80x9d means an alkyl group substituted with a halogen atom, such as, for example, chloromethyl, xe2x80x9cheterocyclylalkylxe2x80x9d means an alkyl group substituted with a heterocyclyl group, such as, for example, pyrrolidinylethyl, wherein, as used above in this paragraph, R is an organic group, Rxe2x80x2 is alkyl and Rxe2x80x3 is H, alkyl or aryl.
The substrate aromatic compound ArX contains an electrophilic atom bonded to leaving group X that is susceptible to the above cross-coupling reaction. As used herein, the term xe2x80x9cnucleophilicxe2x80x9d refers to a chemical moiety having a reactive pair of electrons and the term xe2x80x9celectrophilicxe2x80x9d refers to a chemical moiety that can accept a pair of electrons from a nucleophile.
In a preferred embodiment, Ar comprises a phenyl ring that is substituted on one or more carbons of the ring, wherein each such substituent group is independently selected from substituted or nonsubstituted alkyl, substituted or nonsubstituted alkenyl, substituted or nonsubstituted alkynyl, substituted or nonsubstituted aryl or substituted or nonsubstituted heterocyclyl.
In a more highly preferred embodiment, each of the substituent groups on the phenyl ring of the Ar moiety is independently selected from alkyl, alkenyl, sulfonyl-containing groups, acyclic groups that contain one or more nitrogen heteroatoms per group and heterocyclic groups that contain one 5- or 6-membered heterocyclic ring per group, wherein the heterocyclic ring contains one or two heteroatoms, each independently selected from nitrogen, oxygen and sulfur, per ring and wherein the heterocyclic group may, optionally, be substituted on one or more atoms of the heterocyclic ring. Suitable sulfonyl-containing groups include, for example, alkylsulfate, alkylsulfonate and alkylsulfamoyl. Suitable nitrogen-containing heteroacyclic groups include, for example, cyano, thiocyano, isocyano, alkylthiocyano, alkylcyano, and xe2x80x94(CH2)nxe2x80x94NR3R4, wherein n is a number from 0 to 6, and R3 and R4 are each independently H or (C1-C6)alkyl. Suitable nitroge-containing heterocyclic groups include, for example, pyrrolyl, pyrazolyl, pyridinyl, pyrazinyl, pyrimidinyl, pyridazinyl, pyrrolidinyl, imidazolidinyl, pyrazolidinyl, pyrazolinyl, piperidinyl, piperazinyl, each of which may be substituted or nonsubstituted. Suitable oxygen-containing groups include, for example, pyranyl, furanyl, oxacyclopentyl, oxacyclohexyl, each of which may be substituted or nonsubstituted. Suitable sulfur-containing heterocyclic groups include, for example, thiophenyl, thiacyclohexyl, each of which may be substituted or nonsubstituted. Suitable hereocyclic groups containing two different heteroatoms include, for example, isothiaolyl, isooxazolyl, furazanyl, morpholinyl.
In a more highly preferred embodiment, at least one of the carbon atoms of the phenyl ring of the Ar moiety is substituted with a group selected from (C1-C10)alkyl, cyclo(C4-C6)alkyl, (C2-C6)alkenyl, cyclo(C4-C10) alkenyl and 5- or 6-membered heterocyclic rings that contain one nitrogen heteroatom, each of which may connected to the carbon atom of the phenyl ring via an alkylene bridging group and each of which may be nonsubstituted or substituted, for example, with one or more groups selected from hydroxy, (C1-C6)alkyl (C1-C6)alkoxy and (C1-C6)alkoxycarbonyl.
In a preferred embodiment, X is a halo, sulfonate or phosphonate group, more preferably halo. Preferred sulfonate groups are those according to the general formula: 
wherein R5 is alkyl, aryl, fluoroalkyl, preferably trifluoromethyl, perfluoroalkyl.
Preferred phosphonate groups are those according to the general formula: 
wherein each R6 is independently alkyl or aryl.
The preferred halo group is chloro.
Suitable substrate aromatic compounds include, for example, 4-chloro-N-methylbenzenemethanesulfonamide, 1-bromo-3-cyclohexylbenzene, 4-(2,3-dihydropyran-2-yl)-1-trifluoromethanesulfonatobenzene,1-chloro-2-(2-pyridyl)benzene, 1-chloro-4-[2-(N,N-dimethylamino)ethyl]benzene, 4-chlorobenzonitrile, 1-bromo-4-cyanomethylbenzene,1-chloro-3-(3-hydroxy-1-butyl)benzene, 1-chloro-4-[2-(1-hydroxycyclopentyl)ethyl)benzene, 1-bromo-4-(1-hydroxybut-3-enyl)benzene and 1-methyl-4-hydroxy-(4xe2x80x2-chlorophenyl)-piperidine, 4-(1-aza-methylcyclohex-3-en-4-yl)-1-chlorobenzene. In a highly preferred embodiment, the substrate aromatic compound is 1-methyl-4-hydroxy-(4xe2x80x2-chlorophenyl)-piperidine.
Suitable substrate aromatic compounds are made by known synthetic methods. The substituents on the substrate aromatic compound are selected based on structure of the desired indole product.
In a preferred embodiment, R1 is H, alkyl or aryl, more preferably H.
In a preferred embodiment, each R2 is independently monocyclic cycloalkyl, monocyclic cycloalkenyl or monocyclic aryl, more preferably, phenyl, or, alternatively, the R2 groups are fused to form, together with the carbon atom to which they are each attached, a monocyclic 5- or 6-membered cycloalkyl, cycloalkenyl or aryl ring.
Suitable hydrazones include, for example, benzophenone hydrazone, benzaldehyde hydrazone and cyclohexanone hydrazone. In a highly preferred embodiment, the hydrazone is benzophenone hydrazone.
In a preferred embodiment, reaction of the substrate aromatic compound and the hydrazone is run with an excess of from about 4:1 to about 1.01:1, more preferably from about 2:1 to about 1.05:1, of either the substrate aromatic compound or the hydrazone. In a highly preferred embodiment the reaction of the substrate aromatic compound and the hydrazone is run with an excess of from about 1.5:1 to about 1.1:1 of the hydrazone.
In a preferred embodiment, reaction of the substrate aromatic compound and hydrazone is conducted in the presence of a transition metal catalyst and a base according to the method for transition metal-catalyzed arylation disclosed in U.S. Pat. No. 6,235,936 xe2x80x9cMETAL-CATALYZED ARYLATION OF HYDRAZINES, HYDRAZONES, AND RELATED SUBSTRATESxe2x80x9d to Buchwald et. al., the disclosure of which is hereby incorporated herein by reference.
Suitable transition metal catalysts include, for example, soluble or insoluble complexes of platinum, palladium or nickel, more preferably palladium. Suitable palladium catalysts include, for example, PdCl2, Pd(OAc)2, (CH3CN)2PdCl2, Pd(P(C6H5)3)4, Pd2(dba)3 or Pd(dba)2, wherein xe2x80x9cdbaxe2x80x9d is dibenzylideneacetone, as well as supported palladium, such as palladium on carbon. In a preferred embodiment, the catalyst comprises Pd(OAc)2.
In a preferred embodiment, the catalyst is provided in the reaction mixture as a metal-ligand complex wherein the transition metal catalyst is bound to a supporting ligand. In a preferred embodiment, the ligand is a monodentate alkyl or aryl phosphine or a hybrid thereof, or a chelating ligand, such as for example, alkyl and aryl derivatives of phosphines, biphosphines, amines, diamines, imines, arsines and hybrids thereof.
In a more highly preferred embodiment, the ligand is a phosphine ligand. Suitable phosphine ligands include monodentate phosphine ligands, such as, for example, trimethylphosphine, tripropylphosphine, trisobutylphosphine, tricyclohexylphosphine, trimethyl phosphite, triphenylphosphine. tri-t-butylphosphine, 2-(di-t-butyl-phosphino)biphenyl, 2-(dicyclohexylphosphino)biphenyl, 2-methyl-2xe2x80x2-dicyclohexylphosphinobiphenyl, 2-dimethylamino-2xe2x80x2-dicyclohexylphosphinobiphenyl and 2-dimethylamino-2xe2x80x2-di-t-butylphosphinobiphenyl, and bidentate ligands such as 2,2xe2x80x2-bis(diphenylphosphino)-1,1xe2x80x2-binaphthyl; (xe2x80x9cBINAPxe2x80x9d), 2,2xe2x80x2-bis(dicyclohexylphosphino)-1,1xe2x80x2-binaphthyl, 1,2-dimethylphosphino)ethane, 1,3bis(dicyclohexylphosphino)propane. In a highly preferred embodiment, the ligand is 2-(di-t-butyl-phosphino)biphenyl.
The metal catalyst and ligand may be added to the reaction mixture as separate compounds. Alternatively, a metal ligand complex may be formed prior to addition to the reaction mixture and then added to the reaction mixture as the metal-ligand complex.
In a preferred embodiment, the coupling reaction is run in the presence of a catalytic amount of catalyst. Typically, the amount of catalyst ranges from about 0.0001 to about 20 mole %, more preferably from about 0.05 to about 5 mole %, based on the amount of limiting reactant.
In a preferred embodiment, the reaction mixture includes from about 1 to about 3 equivalents, based on the amount of hydrazone, of a base. Suitable bases include, for example, NaH, LiH, alkoxides such as sodium t-butoxide, sodium 2-methyl-2-butoxide, alkyl metal amides such as sodium amide, alkali metal bis(trialkylsilyl)amides such as lithium bis(trimethylsilyl)amide, tertiary amines such as triethylamine, 4-(dimethylamino)pyridine, alkaline earth carbonates, bicarbonates, hydroxides and phosphates, such as, for example, magnesium bicarbonate, calcium carbonate, potassium carbonate, cesium carbonate and potassium phosphate.
In a preferred embodiment, the reaction of the substrate aromatic compound and the hydrazone is conducted in a liquid reaction medium. The reaction may be run without solvent or, alternatively, may be run in a solvent that is inert under the reaction conditions. Preferably, the solvent is one in which the reaction ingredients, including the catalyst, are soluble. Suitable solvents include aliphatic or aromatic hydrocarbon solvents such as pentane, hexane, benzene, xylene and toluene, ethers such as diethyl ether and t-butyl methyl ether, tetrahydrofuran, 1,4-dioxane and 1,2-dimethoxyethane, esters such as ethylacetate, polar aprotic solvents such as acetonitrile, dimethylsulfoxide, dimethylformamide, dimethylacetamide and 1-methyl-2-pyrrolidinone, halogenated solvents such as dichloromethane, as well as mixtures of two or more solvents. In a highly preferred embodiment, the solvent is an aromatic hydrocarbon or an ether.
In general, the coupling reaction is run under mild conditions that will not adversely affect the reactants, catalyst or product. In a preferred embodiment, the coupling reaction is run at a temperature of from about 25xc2x0 C. to about 300xc2x0 C., more preferably from about 25xc2x0 C. to about 150xc2x0 C.
In a preferred embodiment, the coupling reaction is run in an inert atmosphere, such as, for example, under an argon purge or a nitrogen atmosphere.
In a preferred embodiment, the aryl hydrazone formed in the coupling step is hydrolyzed to form an aryl hydrazine salt according to reaction scheme 2. 
wherein
Ar, R1 and R2 are each defined as in scheme 1 above,
Xxe2x80x2 is halo, acetate, trifluoroacetate, sulfate or phosphate, and
n is a number of from 1 to 5.
In a preferred embodiment, Xxe2x80x2 is halo.
In a preferred embodiment, the hydrolysis is run in a liquid reaction medium comprising water, an alcohol and an acid.
Suitable alcohols include, for example, methanol, ethanol isopropanol or t-butanol. In a preferred embodiment, the alcohol is methanol or ethanol.
Suitable acids include, for example, hydrochloric acid, hydrobromic acid, sulfuric acid, trifluoroacetic acid or phosphoric acid. In a preferred embodiment the acid is hydrochloric acid or sulfuric acid.
In a preferred embodiment, the hydrolysis is run in the presence of from about 2 to about 5 equivalents, based on the amount of hydrazone, of the acid.
In general, the hydrolysis is run under mild conditions that will not adversely affect the reactants or product. In a preferred embodiment, the hydrolysis is run at a temperature of from about 25xc2x0 C. to about 300xc2x0 C., more preferably from about 25xc2x0 C. to about 150xc2x0 C.
In a highly preferred embodiment, the aryl hydrazone is treated with a mixture of water, ethanol and hydrochloric acid at reflux to yield the hydrochloric acid salt of the desired hydrazine.
In a preferred embodiment, the substituted indole compound is formed by an acid catalyzed reaction of the aryl hydrazone with a ketone or an aldehyde.
In a highly preferred embodiment, the substituted indole compound formed from the aryl hydrazine via an acid-catalyzed Fischer indole cyclization reaction according to reaction scheme 3: 
wherein:
Ar, R1 and Xxe2x80x2 are each defined as in scheme 1 above,
R7 is substituted or nonsubstituted alkyl, substituted or nonsubstituted alkenyl, substituted or nonsubstituted aryl or substituted or nonsubstituted heterocyclyl,
R8 is H, substituted or nonsubstituted alkyl, substituted or nonsubstituted alkenyl, substituted or nonsubstituted aryl or substituted or nonsubstituted heterocyclyl, and
nxe2x80x2 is a number of from 1 to 5.
In a preferred embodiment, R7 is substituted or nonsubstituted nitrogen-containing heteroacyclic group, more preferably a group according to xe2x80x94(CH2)nxe2x80x94NR3R4, wherein n, R3 and R4 are each as described above, or a heterocyclic moiety according to:
xe2x80x94(CH2)mxe2x80x94A
wherein:
m is a number from 0 to 6, and
A is a nitrogen-containing heterocyclic group that contains one 5- or 6-membered heterocyclic ring per group, wherein the heterocyclic ring contains one or two nitrogen heteroatoms per ring and wherein the heterocyclic group may, optionally, be substituted on one or more atoms of the heterocyclic ring, with for example, (C1-C6)alkyl.
In a more highly preferred embodiment, R7 is aminoalkyl such as aminoethyl, alkylaminoethyl such as methylaminoethyl, dialkylaminoalkyl, such as dimethylaminoethyl, pyrrolidinyl, pyrrolidinylalkyl such as pyrrolidinylethyl, alkylpyrrolidinylalkyl such as methylpyrrolidinylmethyl, pyridyl, alkylpyridyl such as methylpyridyl, piperidinyl, piperidinylalkyl such as piperidinylmethyl or alkylpiperidinyalkyl such as methylpiperidinylmethyl.
Suitable ketones include, for example, phenylacetone, cyclohexanone, ethyl pyruvate, 2-nonanone, and acetophenone.
Suitable aldehydes include, for example, 4-chlorobutyraldehyde, ethyl glyoxalate, hept-5-en-1-al, 4-piperidinylacetaldehyde, 3-cyclohexylpropionaldehyde, phenylacetaldehyde, 3-(2-N-methylpyrrolidinyl)propionaldehyde, 4-(1-pyrrolidinyl)butyraldehyde, and 4-(N,N-dimethylamino)butyraldehyde, and may be formed in situ from an aldehyde precursor, such as, for example, an acetal or bisulfite adduct. Suitable acetals include, for example, acetals such as 4-(N,N-dimethylamino)butyraldehyde diethyl acetal or 4-(N,N-dimethylamino)butyraldehyde dimethyl acetal. Suitable bisulfite adducts include, for example, 4-chloro-1-hydroxybutanesulphonic acid sodium salt.
In a preferred embodiment, dimethylaminobutyraldehyde is formed in situ from 4-(N,N-dimethylamino)butyraldehyde diethyl acetal or 4-(N,N-dimethylamino)butyraldehyde dimethyl acetal.
In a preferred embodiment, the indole synthesis reaction is run in the presence of from about 1 to about 5 equivalents, more preferably from about 1 to about 2 equivalents, aldehyde or aldehyde precursor, based on the amount of hydrazine.
Suitable acids include hydrochloric, hydrobromic acid, sulfuric acid, trifluoroacetic acid and phosphoric acid. In a preferred embodiment, the acid is sulfuric acid or phosphoric acid. In a preferred embodiment, the indole cyclization reaction is run in the presence of from about 0.5 to about 2 equivalents, more preferably from about 0.8 to about 1.2 equivalents acid, based on the amount of hydrazine.
In a preferred embodiment, the indole cyclization reaction is run in a liquid reaction medium. In a preferred embodiment, the indole synthesis reaction is conducted in a suitable solvent, such as water, alcohol or a mixture thereof.
In a preferred embodiment, the indole cyclization reaction is run under mild conditions that will not adversely affect the reactants, catalyst or product. In a preferred embodiment, the coupling reaction is run at a temperature of from about 25xc2x0 C. to about 250xc2x0 C., more preferably from about 25xc2x0 C. to about 150xc2x0 C.
The indole product may then be isolated and purified by known techniques.
In a highly preferred embodiment, a substituted aryl halide is made via a Grignard reaction and metal-catalyzed arylation of benzophenone hydrazone with the substituted aryl halide is followed by hydrolysis to give to give a substituted aryl hydrazine. The aryl hydrazine then undergoes acid-catalyzed Fischer indole synthesis to give the 5-(1-Aza-1-methylcyclohex-3-en-4-yl)-3-[2-(N,N-dimethylamino)ethyl)]-1H-indole product.
The method of the present invention is useful for making a wide variety of substituted indole compounds, such as for example, those substituted indole compounds which have been found to act on 5-HT1-like receptors and to be useful in the treatment of certain medical conditions, as disclosed, for example, in U.S. Pat. No. 5,607,960, xe2x80x9cINDOLE DERIVATIVES AS 5-HT1-LIKE AGONISTS FOR USE IN MIGRAINExe2x80x9d to Wythes and U.S. Pat. No. 5,998,438, xe2x80x9c5-CYCLO INDOLE COMPOUNDSxe2x80x9d to Slassi et. al., the respective disclosures of which are hereby incorporated herein by reference.
Exemplary substituted indole compounds include: 3-[2-N,N-dimethylamino)ethyl]-5(tetrahydropyran-2-yl)-1H-indole, 3-[2-(N,N-dimethylamino)ethyl]-5-(1-thiacyclohex-4-yl)-1H-indole, 5-(1-aza-1-tert-butoxycarbonylcyclohex-3-en-4-yl)-3-[(N-methylpyrrolidin-2-yl)methyl]-1H-indole, 5-(1-aza-1-benzylcyclohex-3-4yl)-3-(2-pyrrolidinylethyl)-1H-indole, 5-(1-aza-1-methyl-4-hydroxycyclohex-4-yl)-3(2-pyrrolidinylethyl)-1H-indole, 5-(1-aza-1-tert-butoxycarbonyl-4-hydroxycyclohex-4-yl)-3-(2-pyrrolidinylehtyl)-1H-indole, 5-[2-hydroxycyclopentyl)ethyl]-3-[N-[2-(N,N-dimethylcarbamoyl)ethyl]-2(R)-pyrrolidinylmethyl]-1H-indole, and 5[2-(1-hydroxycyclopentyl)ethyl]-3-(2(R)-pyrrolidinylmethyl)-1H-indole.